Powered pipe tongs are well established in the art and, for well drilling use, they have evolved with many common characteristics. Back-up tongs do not rotate and their construction can take forms not dictated by rotating machinery. Tongs that rotate pipe carry the pipe gripping dies on the rotating machinery and the die loading elements rotate with pipe. It is common to load the dies with cams on a main drive ring. To allow the dies to be loaded by the cams, the cams are commonly mounted on a die carrier which is held stationary by a brake on the tong frame until the main drive ring has rotated enough to drive the dies toward the pipe with enough force to rotate the pipe. Most power tongs that rotate have radial openings to allow the tongs to be removed from the pipe. The radial openings may be called throats or gaps. The gaps are in the frame, main drive ring and die carrier. In such cases, the main drive ring is called a partial ring. The die carrier is called a partial ring.
In conventional power tongs, the cam angle is designed to apply enough radial loads to pipe to grip the pipe and not slip when proportional torque is applied to the pipe. If the pipe requires little torque when turning begins, the dies do not apply much radial gripping force. This light force allows the tong to wobble about as turning proceeds and the dies then "chew" on the pipe surface and cause damage.
If the dies are initially loaded with the maximum force required to complete the rotational excursion of working one connection, the dies do not "chew". The die gripping force does not damage as a consequence of time of gripping and damage is reduced. The cam and brake arrangement does not lend itself to precision die loading force control.
It is therefore an object of this invention to use force producing means on the tong frame to close and load pipe gripping dies, the forcing means then to remain stationary when the rotating machinery turns with pipe.
It is another object of this invention to provide means in the rotating machinery to store energy to carryout the rotating function without relaxing grip on pipe.
It is still a further object of this invention to provide apparatus to grip and rotate pipe that may be released from the pipe in any rotational position of the apparatus.
It is yet another object of this invention to provide pipe rotating machinery and frame mounted force means to actuate pipe gripping dies, that can be fitted to existing tong frames of conventional design.
These and other objects, advantages, and features of this invention will be apparent to those skilled in the art from a consideration of this specification including the attached claims and appended drawings.